This invention relates generally to the field of hard disc drive data storage devices, and more particularly, but not by way of limitation, to a voice coil magnet spacer positioned so as to facilitate in-deck merging of the actuator.
Disc drives of the type known as xe2x80x9cWinchesterxe2x80x9d disc drives, or hard disc drives, are well known in the industry. Such disc drives magnetically record digital data on a plurality of circular, concentric data tracks on the surfaces of one or more rigid discs. The discs are typically mounted for rotation on the hub of a brushless DC spindle motor. In disc drives of the current generation, the spindle motor rotates the discs at speeds of up to 15,000 RPM.
Data are recorded to and retrieved from the discs by an array of vertically aligned read/write head assemblies, or heads, which are controllably moved from track to track by an actuator assembly. The read/write head assemblies typically consist of an electromagnetic transducer carried on an air bearing slider. This slider acts in a cooperative hydrodynamic relationship with a thin layer of air dragged along by the spinning discs to fly the head assembly in a closely spaced relationship to the disc surface. In order to maintain the proper flying relationship between the head assemblies and the discs, the head assemblies are attached to and supported by flexures attached to the actuator.
The actuator assembly used to move the heads from track to track has assumed many forms historically, with most disc drives of the current generation incorporating an actuator of the type referred to as a rotary voice coil actuator. A typical rotary voice coil actuator consists of a pivot shaft fixedly attached to the disc drive housing base member closely adjacent the outer diameter of the discs. The pivot shaft is mounted such that its central axis is normal to the plane of rotation of the discs. An actuator bearing housing is mounted to the pivot shaft by an arrangement of precision ball bearing assemblies, and supports a flat coil which is suspended in the magnetic field of an array of permanent magnets, which are fixedly mounted to the disc drive housing base member. These magnets are typically mounted to plates, or xe2x80x9cpole piecesxe2x80x9d which are held in positions vertically spaced from another by spacers at each of their ends.
On the side of the actuator bearing housing opposite to the coil, the actuator assembly typically includes a plurality of vertically aligned, radially extending actuator head mounting arms, to which the head suspensions mentioned above are mounted. These actuator arms extend between the discs, where they support the head assemblies at their desired positions adjacent the disc surfaces. When controlled DC current is applied to the coil, a magnetic field is formed surrounding the coil which interacts with the magnetic field of the permanent magnets to rotate the actuator bearing housing, with the attached head suspensions and head assemblies, in accordance with the well-known Lorentz relationship. As the actuator bearing housing rotates, the heads are moved generally radially across the data tracks of the discs along an arcuate path.
The discs, actuator and voice coil magnets are mounted inside a housing, also known as a deck, along with all the other necessary components. Installation of the discs, magnets and actuator can be problematic, especially when the deck is of a tub-type casting having a floor and upstanding walls. When the actuator is fully installed, the arms and head must be positioned between the discs while the coil should be positioned between the magnets. It should be apparent that the actuator pivot and magnet spacers prevent the actuator from being moved laterally into its installed position, while preinstalled discs and magnets would also obstruct the actuator if it were lowered into its installed position. It has therefore been necessary for drive manufacturers to implement procedures for xe2x80x9cmergingxe2x80x9d the magnets, discs and actuator as they are placed into the deck.
One way in which this has been accomplished in the past is by using machinery to properly position the magnets, discs and actuator relative to one another, and then lowering the resulting subassembly into the deck. However, this operation requires the use of specialized assembly equipment which is costly to create, maintain and operate.
Another way in which this problem has been solved in the past is by first installing the discs and the lower magnet plate in the deck before mounting the actuator on its pivot, with the actuator rotated into an off-disc position such that the discs do not interfere with its downward movement. The actuator can then be rotated into its installed position, and all that remains is to install the upper magnet above the coil. However, this final step gives rise to additional problems, because of the difficulties involve with installing the spacers between the magnets. On one hand, if the spacers are mounted to the lower magnet before it is mounted in the deck, the locations of the spacers will obstruct the actuator if an attempt is made to lower it into its off-disc position. On the other hand, it is very difficult as a mechanical matter to mount the spacers to a lower magnet which has already been installed in the deck. Manufacturers have reacted to this further problem by eliminating the spacers altogether. This is done, for example, by providing an upper pole piece which is bent downwardly and then outwardly at its ends, so the ends of the upper pole piece may be mounted directly to the ends of the lower pole piece. However, this requires that the upper and lower pole pieces be of different shapes, raising additional problems. For example, fabrication of upper and lower pole pieces of different shapes requires additional tooling, which in turn increases costs. Moreover, the bends in the upper plate can alter the magnetic field between the magnets. This causes the directions and magnitude of the magnetic field to be unpredictable, possibly resulting in a decrease in drive performance.
What the prior art has been lacking is a drive structure which allows its components to be easily assembled without requiring the use of excessive assembly machinery and without diminishing drive performance.
Disclosed is a voice coil magnet and spacer arrangement. Upper and lower magnets and/or pole pieces are arranged so as to allow a spacer to be located beyond the coil end of the actuator, thereby facilitating in-deck merging of the actuator with the discs and magnets. Additional features and benefits will become apparent upon a review of the attached figures and the accompanying description.